1. Field of the Invention
The present invention relates to fiber-reinforced polymeric foam composites and their manufacture.
2. Description of Related Art
Polymeric foam composites comprise a polymeric foam sandwiched between facing materials. Polymeric foam composites are useful as wall and ceiling panels in a wide variety of structures to provide thermal and acoustical insulation, fire retardation, and structural rigidity. Manufacturing polymeric foam composites typically involves disposing a foamable mixture between two continuous conveying sheets of facing materials and then foaming the foamable mixture into a polymeric foam.
A desirable polymeric foam composite contains fibers dispersed within the polymeric foam (a fiber reinforced polymeric foam). Fiber reinforced polymeric foams can have enhanced physical and performance properties such as increased thermal dimensional stability, strength and fire resistance. One way to prepare a polymeric foam composite containing a fiber reinforced polymeric foam is by conveying an expandable fiber mat filled with foamable mixture between the two sheets of facing material and then expanding the foamable mixture into a polymeric foam. The expandable fiber mat expands with the foamable mixture during the foam forming step. Unfortunately, there are weaknesses associated with current expandable fiber mat technology.
Expandable fiber mats contain a binder that holds them together during processing. Generally, fiber mats having a binder level above six percent by weight of binder and fiber (i.e., based on total mat weight) require mechanical fracturing of the fibers or binder in the mat in order to render the mat expandable. Such mechanical fracturing typically involves corrugation (e.g., crimping or crinkling) of the fiber mat. Corrugating a fiber mat can cause it become sufficiently inhomogeneous in its composition so as to cause ridges or necking, often resulting in polymeric foam composites that can have a non-uniform appearance. Additionally, because corrugation is typically an operator controlled process step, inconsistency in the extent of corrugation (and hence, inconsistency in fiber dispersion in the polymeric foam) can occur during fabrication, particularly when operator shifts change.
Low binder fiber mats (fiber mats containing less than six percent binder, based on total mat weight) are desirable because they are expandable without requiring corrugation. Unfortunately, low binder fiber mats are difficult to implement in standard fabrication processes. For example, a low binder fiber mat tends to bind to itself when in a roll, causing the mat to pull apart upon unrolling. Low binder fiber mats also tend to coat roller(s) that they contact with loose fibers. As a result, roller(s) require frequent cleaning or the fibers coating the roller(s) can cause low binder fiber mats to pull apart as they travel over the roller(s). Additionally, low binder fiber mats tend to have insufficient tensile strength to suitably convey in a continuous polymeric foam composition fabrication process.
A process for preparing polymeric foam composites that uses a low binder fiber mat but does not experience the aforementioned difficulties associated with low binder fiber mats is desirably.